Multi-Parametric Approach for Earthquake Precursor Detection in Assam Valley (Eastern Himalaya, India) using Satellite and Ground Observation Data

Abstract

Abstract In present study soil radon (Rn-222) emanation, geomagnetic total field intensity (Btotal), and total electron content (TEC) in ionosphere prior to Mw 5.5, Kokrajhar, Assam earthquake of September 12, 2018 were investigated using multiparametric geophysical observations at Ouguri Hills, Tezpur, Assam. Prominent anomalies were observed in the soil Rn-222 emanation, Btotal and TEC time series prior to the event and are discussed. It was observed that soil Rn-222 persisted anomalies 50 days prior to the earthquake event. The correlation coefficient between soil Rn-222 with soil temperature and soil pressure was estimated to be feeble, 0.2 and –0.4 during the investigation period. Similar anomalies were observed 26 days prior to the earthquake event in Btotal. The ionospheric TEC also persisted anomalies 17 days prior to the event. The amount of anomalous values observed for soil Rn-222, Btotal, and ionospheric TEC ranged between –15.61 to 25.02 KBq/m3, –83.33 to 10.50 nT and –13.06 to 7.09 TECU below LB and above UB respectively. An increase of 1.92 nT and a decrease of –36.77 nT of daily rate change was observed during the anomaly period compared to the normal days. The study revealed possibility of precursor detection through multi parametric approach from ground to ionosphere level.